From the online wiki article on lock picking. --VM44
Another technique, often the fastest, uses a vibration pick or gun, which sharply strikes all the bottom pins simultaneously while light torque is applied; like a cue ball, the energy is transmitted through to the top pins, which fly to the top of their well. This momentarily creates a large space between the two pins, and, given the right timing, the lock can be turned. The Pick Gun was initially developed for law enforcement, allowing officers who are not adept at lock picking to open a lock quickly and easily.
A refinement of this kinetic technique is the use of bump keys. These are keys with all the cuts at or slightly below the deepest level for a key made by the manufacturer, and a small amount of material removed at the tip, and, where applicable, at the shoulder - the part of the key that prevents the key from entering the lock too deeply. By sharply striking the bump key, it is possible to apply an even impact to each pin column, which then separates as if struck using a pick gun. Bump keys will work in many locks that pick gun needles will not fit into.
To defend against these attacks, high-security locks use a sidebar, which engages from another axis and also prevents the lock from turning. Medeco locks do this by requiring the pins to be rotated to a correct position, as well as moved to their correct height. Other brands put the sidebar cuts in the side of the key.